Recently, wireless LAN technologies are advancing in three directions. In an effort to further increase a transfer rate as extensions in the evolution of the existing wireless LAN, IEEE (institute of electrical and electronic engineers) 802.11ac and IEEE 802.11ad have been introduced. IEEE 802.11ad is a wireless technology using a 60 GHz band. Also, in order to allow for wider area transmission in terms of distance, relative to the existing wireless LAN, a wide area wireless LAN utilizing a frequency band less than 1 GHz has recently been emerged, which includes IEEE 802.11af utilizing a TVWS (TV white space) band and IEEE 802.11ah utilizing a 900 MHz band. These schemes aim at extending an extended range Wi-Fi service, as well as a smart grid and a wide are sensor network. Also, an existing wireless LAN MAC (medium access control) technology has a problem in that an initial link setup time is very lengthened according to circumstances. In order to solve the problem, 802.11ai standardization activity has been actively ongoing to allow a station (STA) to quickly access an access point (AP).
IEEE 802.11ai, a MAC technology handling a prompt authentication procedure to remarkably reduce an initial setup and association time of a wireless LAN, was started to be standardized in January 2011 by a formal task group. In order to allow for a rapid access procedure, IEEE 802.11ai is under discussion to simplify a procedure in regions such as AP discovery, network discovery, TSF (time synchronization function) synchronization, authentication & association, merging of a procedure with a higher layer, and the like. Among them, ideas such as procedure merging utilizing piggyback of DHCP (dynamic host configuration protocol), optimization of full EAP (extensible authentication protocol) using a concurrent IP, effective selective AP scanning, and the like, has been actively discussed.